Electrochemical inhibit gate

ABSTRACT

An inhibit gate for data processing systems utilizing electrochemical waves of polarization as the basic signalling mechanism employing a pair of electrodes immersed in an electrolyte is disclosed. The inhibit gate employs preferably iron and gold as the active materials in an electrolyte of nitric acid. Inhibit operation is achieved by the particular composition, size and placement of two electrodes. In one form, the inhibit gate exhibits adaptive properties.

United States Patent Robert M. Stewart Encino, Calif. 673,252

Oct. 2, 1967 May 18, 1971 inventor Appl. No. Filed Patented Assignee ElMonte, Calif.

Aerojet-General Corporation ELECTROCHEMICAL INHIBIT GATE 7 Claims, 6Drawing Figs.

U.S. Cl

Int. Cl

Field O'r'sZJiQIIIIIIIIII."""IIII 204/5, 340/ 172.5 Gllc 13/02 340/173;204/5 (Cursory) [56] References Cited UNITED STATES PATENTS 2,708,7485/1955 Straube 340/173 3,222,654 12/1965 Widrow... 340/173 3,482,21712/1969 Finney 340/173 Primary Examiner-Terrell W. Fears Attorneys-JohnE. Wagner and Edward O. Ansell PATENTEnumslen 2 fi m m|J\\ .l 3 A Tm wvs N 4 WM w 0 t w m k w lr a P H R W1. a aw w m" m 2 mm I C m D V mm VA/ W 14 Fig.1

Fig. 3 ,Electrolyte fillad Reaction Reglon ELECTROCHEMICAL INHIBIT GATEBACKGROUND OF THE INVENTION This invention relates to electrochemicalcomputers and more particularly to electrochemical inhibit gates.

In my previous US. Pat. No. 3,149,310, I demonstrated that in arelatively homogeneous structure of iron particles immersed inconcentrated nitric acid in which we can produce complex electrochemicalwaves upon multielectrode stimula tion, through the systematicapplication of electric fields across the entire structure,charge-transfer can be effected in restricted regions (those associatedwith recent activity) thereby making possible semipermanent reversibleplastic changes in fine structure and, therefore, functioning. In my US.Pat. No. 3,295,112, I also illustrated how certain simple discrete logicelements may be produced in an electrochemical system and how they maybe formed into a truly fieldtrainable" adaptive computer. I disclosed inthe latter patent a structured inhibit gate employing three dipolemembers in a dual chambered housing. In my copending application, Ser.No. 504,893, filed Oct. 24, I965, and now abandoned, I illustrate asimple nondestructive readout active wave-circulation memory device,parity check and other logic elements using similar materialscorresponding signals to this invention in a different physicalconfiguration.

SUMMARY OF THE INVENTION In the field of electrochemical computers,there is a need for a simple, logically complete discrete element whichcan form the basis of more complex computing systems. I have devisedanother form of inhibit gate employing an even simpler structure thanthat disclosed in U.S. Pat. No. 3,295,112 and which can be used singlyor replicated to generate additional combinational functions of completegenerality.

Basically, the inhibit gate of this invention involves a pair of similarrods or wires of material which exhibits the property of passivation inthe presence of an electrolyte and excitation responsive to an externalstimulus. The rods or wires are in generally parallel relationship withthe first wire extending beyond the end ofthe second element. In thefirst structure successfully tested, the latter terminates in a helicalportion of inexcitable material encircling the first wire and spacedtherefrom, but, in general need only come close to the first memberalong a sufiiciently large area.

Input-exciting connections are made with each of the rods, and thelonger first one is coupled to an output device. In operation, any inputpulse to the longer element is conducted to the output unless asimultaneous pulse appears at the shorter or inhibit element inclassical inhibit gate operation.

In another embodiment of this invention, the longer or control electrodeis coupled through parallel excitatory electrochemically adaptiveportions to a separate output electrode as in U.S.Pat. No. 3,295,112.

BRIEF DESCRIPTION OF THE DRAWING This invention is described in moredetail below and is illustrated by the drawing in which:

FIG. 1 is a simplified sectional view through a single inhibit gate inaccordance with this invention;

FIG. 2 is a schematic diagram of the device of FIG. 1;

FIG. 3 is a simplified sectional view of cascaded logic elements basedupon the structure of FIG. 1;

FIG. 4 is a schematic diagram of the cascaded logic elements of FIG. 3;

FIG. 5 is a schematic diagram of another form of cascaded logic elementemploying the basic structure of FIG. 1; and

FIG. 6 is a simplified showing of an adaptive computer element using theprinciples of this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Now referring to FIG. 1, anelectrochemical computer element may be seen therein which is capable ofoperating as an inhibit gate. It employs two active elements I0 and 11preferably iron wires or fibers immersed in an electrolyte which fills ahousing 12. The iron element 11 is shorter than element I0 and includesan inexcitable tail or dendrite 11a which encircles, but does not touch,the element 10. The elements 10 and II are mechanically supported in thehousing 12 in spaced parallel relation by insulating chemically inertmeans unshown in the drawing but which may constitute inert particulatematerial such as particles of glass. Each element 10 and 11 is inintimate contact with the electrolyte such as 50-70 percent concentratednitric acid which reacts with the surface of the elements 10 and 11 toform stable passivated coating but which then subsequently virtuallyterminates further'chemical reaction between the acid and the elementsuntil stimulated. This coating remains passive indefinitely unlessdisturbed by mechanical shock, local chemical reaction, intense light orheat or the application of an electrical pulse which causes a localbreakdown of the passive coating. The local region of chemical activitybetween the iron and nitric acid upon the application of such stimuli isprogressively transmitted along the length of the element 10 as a localactive region. This local region or pulse may be observed visually andalso detected by the resultant transient change in local electric fieldwhich usually results in about 0.7 v. change in potential differenceacross the surface. A pair of spaced probes l8 and 19 connected to ameter 20 for detecting such field changes constitutes a typical outputdevice of a system using the inhibit gate. For purposes of illustration,the triggering source for element I0 is illustrated as an electricalpulse source 14, triggered externally over lead I5 and applying thepulse across the passivated film on the surface of element 10. Theelectrochemical reaction described briefly above is explained in moredetail in my US. Pat. No. 3,149,310 which should be reviewed if moreadequate understanding of the phenomenon is required. Sufiice it to saythat a detectable pulse may be transmitted with some characteristicdelay by electrochemical reaction from an input to an output region.

I have now discovered that such pulse transmission along such a linearmember may be controllably suppressed by means of an adjacent excitable"dipole in the region of the inexcitable but conductive member. For thisreason, the second electrode 11 of excitable material such as ironincludes a tail 11a of inexcitable material such as gold or silver. Thetail Ila encircles the element I0 between its input region at the leftand output region at the right to be in proximity to the path of pulsetransmission along element 10. Element 11 has an associated inpu'rpulsegenerator 16 which is triggered by remote source denoted by arrow 17comparable to the lead 15 of element I0. In the absence of any pulse onelement 11, the passage of pulses from input to output of element 10 isnot impeded. However, a pulse on the element 11 from a pulse generator16 reaching the tail portion 11a produces an electric field andcirculation of current which suppresses and obliterates any pulsetraveling through the encircled inhibition region of element 10.

A schematic diagram of the device is shown in FIG. 2. The primary ordirect input signal source is identified by the encircled y and thedirect signal path between the input source y and output by the arrowheads on the element 10. The inhibit element 11 responds to the x-inputsignal to the gate and is coupled to the element 10 to inhibit pulsetransmission between the input and output ends of element 10.

The device of FIGS. 1 and 2 therefore exhibits both signal conductionand inhibition or produces in the script of Boolean algebra thefunction:

R=x'y, or the device responds with input and y and not x, where Rdenotes response of the output detector or meter 20, x' denotes thelogical inverse or complement of an input signal from pulse generator16, and y denotes an input signal from source 14 to element 10.

A variation on the operation of the basic inhibit gate of FIGS. 1 and 2may be produced by:

l. the addition of additional inhibit inputs;

2. the substitution of a source of constant excitation for the pulsesource 14 of FIG. 1 to provide a simple invertor or complementationdevice;

3. additional inputs and constant excitation to give generalized Peircefunction or NOR gate as in FIGS. 3 and 4;

4. to provide variable or adaptive coupling;

5. cascaded elements to perform more complex functions.

Examples of logic devices incorporating multiple inhibit inputs (l) andsources of constant excitation (2) are shown in FIGS. 3, 4 and 5. FIG.3, similar to FIG. I, shows a simplified structural embodiment of an NORgate with a number of excitable elements 21-25 each with a respectiveinput signal source 26-30. The element 24 constitutes thesignal-conductive path comparable to the element 10 of FIG. 1, andelements 21, 22, 23 and 25 are multiple-inhibit inputs. The signalsources for elements 26-28 and 30 are represented by the letterdesignations w, x, y and z to facilitate the development of theoperational equation of the device. The signal source 29 of thisembodiment is a free-running pulse generator represented by the numerall to indicate that it produces a constant operating signal input to thedevice, and in the absence of any inhibiting input, produces one-to-oneconcurrence of output pulses. The output pulses are detected by probes31 and 32 connected to utilization device 33 similar to the detector 20of FIG. I. The chamber, of course, enclosed an electrolyte whichestablishes the passivated condition on the active elements and allowsthe excitation and signal conduction phenomena to occur.

A schematic of the device of FIG. 3 is shown in FIG. 4 and as can beseen, rather closely represents it in physical, as well as functional,configuration. As so constructed, the device exhibits the property of:

R=wx'y0:z'

or in other words, a generalized Peirce function or NOR gate. Devices ofthis type may be replicated in a plurality of layers as exemplifiedschematically in FIG. illustrating a two-layer system. It includes threeinhibit inputs 40, 41 and 42 driven by sources at, y and 1 respectivelyand two constantly excited inputs 43 and 44 driven by excitory sources1,, and I respectively. The input 43, although excitory, is coupled asan inhibitory input to the element 44. The x-input 40 serves totemporarily disable the inhibit input 43. The inhibit inputs y and zoperate in the same manner as the inhibit element in FIGS. 1 and 3 withthe net result that the device of FIG. 5 exhibits the property:

R (xI ly ill It is apparent from these embodiments that through multiplelayers, it is possible to realize any minterm of input variables, i.e.,a device which responds to one and only one specific input pattern.

Conditionable coupling or conditioned response may be accomplished inaccordance with this invention employing the embodiment of FIG. 6. Itincludes a housing 50 enclosing an members.

I training of electrochemical computing elements of this type is taughtin my previous US. Pat. No. 3,149,310, but briefly it utilizes thephenomenon that the-iron surface impedance of an element drops by afactor of at least 400 during and for a short period after excitation.Therefore, an electric field applied across the electrodes 56 and 57after firing of electrode 51 and response of one or more of the outputelectrodes 53, 54 or 55 will increase primarily (or decrease dependingupon field polarity) the size of the dendrite structure of recentlyfired electrodes by electrodeposition or depletion, thereby changing thecoupling to the response member. For example, the normal response of theassembly of FIG. 6 is:

indicating that one or more of the responder or output electrodes 53,54, or 55 will produce an output pulse in the absence of a pulse on thexinhibit electrode 52.

If the response occuring is unwanted, the application of a fieldpotential across the field electrodes 56 and 57 will result in partialdepletion of the recently fired responder elements while leaving theremaining unfired responders virtually unaffected. The process of fieldconditioning comprises the steps of l applying an input pulse andmonitoring the output; (2) if change desired, repeat with-immediateapplication of field shock; (3) reapply input to check for properlychanged response. Repeat (2) and (3) until the desired response isachieved. With the addition of field trainable response, the operationof the assembly of FIG. 6 may be characterized as:

where s,, s s are the effectively binary (0, 1) states of coupling ofthe signal source'(inverted) to each of the output It is apparent thateach of the logic assemblies described input electrode 51, an inhibitelectrode 52 and a number of output electrodes 53, 54 and 55. There arethree significant differences in this embodiment from the previouslydescribed devices. First, there are multiple output elements, eachhaving a grown extension or dendrite extending into a lower reactionregion. This region is embraced by a pair of field electrodes 56 and 57having external terminals 60 and 61 through which a field potential maybe applied to the reaction region. The housing 50 is filled with anelectrolyte such as concentrated nitric acid producing the primaryreaction and, in addition, a soluble salt of a metal from which metallicions may be prime advantages are achieved when replicated intomultilevel or pyramidal assemblies to provide a single binary responseto complex input functions. An example of a requirement for suchresponse is in pattern recognition systems.

I claim:

1. An electrochemical gate, comprising:

a plurality of electrodes;

an electrolyte in which said electrodes are immersed and reactive withsaid electrodes to form on each of their surfaces a passive film;

a plurality of energizers for said electrodes to cause breakdowns atspecific areas in their films which breakdowns travel along theirsurfaces; 1

a plurality of detectors to sense the breakdowns at other specific areasof said electrodes;

coupler means for the output of at least one said detector to at leastone other said electrode;

synchronizer means for said energizers; and

means to interconnect said couplers and synchronizers so that a signalrepresenting a desired excitation combination thereof is provided at theoutput of at least one said detector.

2. The gate of claim 1 wherein each said coupler is effective at areasof each said electrode other than the specific areas affected by eachsaid energizer.

3. The gate of claim 1 wherein each said detector and coupler comprisesan extension attached to said electrode and nonreactive with saidelectrolyte.

4. The gate of claim 1 wherein each said coupler comprises a windingaround said electrode, but out of physical contact therewith.

vide a signal representing a NOR function.

7. The gate of claim 3 wherein each said electrode is of iron,

said electrolyte is nitric acid pler is of noble metal.

and each said detector and cou-

2. The gate of claim 1 wherein each said coupler is effective at areasof each said electrode other than the specific areas affected by eachsaid energizer.
 3. The gate of claim 1 wherein each said detector andcoupler comprises an extension attached to said electrode andnonreactive with said electrolyte.
 4. The gate of claim 1 wherein eachsaid coupler comprises a winding around said electrode, but out ofphysical contact therewith.
 5. The gate of claim 1 wherein saidinterconnections provide a signal representing an inhibit function. 6.The gate of claim 1 wherein said interconnections provide a signalrepresenting a NOR function.
 7. The gate of claim 3 wherein each saidelectrode is of iron, said electrolyte is nitric acid and each saiddetector and coupler is of noble metal.